This application is for support of a training program in Allergy and Clinical Immunology for post-doctoral medical and pediatric trainees at Yale University School of Medicine. There is a double training faculty of firstly, clinician-researchers in the Department of Medicine, in the Sections of Allergy, Clinical Immunology, Rheumatology, and Infectious Diseases, and also in Pediatrics; and a basic sciences immunology training faculty in the Department of Immunobiology. The faculty's expertise spans nearly all of the areas important to allergy and clinical immunology, and modern immunology, including: cellular, molecular, biochemical, antigen- processing, presenting, and signaling research. There are several faculty with special expertise in Lyme disease, that was discovered at Yale by one of our fellows under this training program. There is comprehensive training in both medical and pediatric aspects of Allergy, and Clinical immunology, as well as Rheumatology, Dermatology, Gastroenterology. Pulmonary, and ENT. The group is well equipped with major instruments including: 3 cytoflourographs, an oligonucleotide synthesizer, peptide protein sequinator and numerous gamma and beta counters, and diverse computers. This is a small training program with a large faculty taking only one new fellow per year, emphasizing the need for a minimum of 3-5 years laboratory training for preparation for positions in research medicine. The faculty have a strong record in training, collaborative research; especially training of individuals under this Allergy and Clinical Immunology Training Grant. The fellows spend most of their first year engaged in various clinical activities, and the second and third years are spent almost entirely in the laboratory under the guidance of a mentor developing an individual research program, while taking various immunobiology courses, participation in weekly seminars and journal clubs, and regularly giving talks on their research, and on subjects of mutual interest. In summary, the program offers a unique and high quality basis for superb training of outstanding candidates for future positions in academic medicine and pediatrics, and as such as been most successful over more than 25 years of continuous funding.